Estimates of the number of people who have been able to sign up for Obamacare since enrollment began more than two weeks -- which has been hampered by difficulties in accessing the main federal website -- are beginning to emerge, according to Fox News. And, while the federal government hasn’t released its own enrollment figures, analysts and private firms have been reporting their own findings.

The Advisory Board, a research and consulting firm, has tracked enrollment since it began Oct. 1, and according to its Daily Briefing website, at least 50,082 people picked a plan through 15 state-based exchanges, or SBEs, and that at least 183,088 had applied for coverage.

Several state insurance exchanges have reported strong interest in Obamacare from those under the age of 35, a key demographic widely considered critical to the implementation of the Affordable Care Act, Modern Healthcare reported, according to the Advisory Board.

In October, officials from Maryland Health Connection, a state online marketplace, announced that the most common age group among its initial 25,000 verified accounts was 25 to 29, the Advisory Board noted. Altogether, 36 percent of the verified accounts were created by individuals under 35. And officials from Access Health CT -- Connecticut's exchange -- said nearly a third of the state's initial 1,157 applicants were under 35. It’s not clear whether the young adults' interest also applies to all state exchanges, or if the same trend is being noticed among applicants in the federal exchanges.

U.S. Health and Human Services, or HHS, officials have said they will not release enrollment data for the federal insurance marketplaces currently operating in 36 states.

Nevertheless, enrollment has been hampered by the ability to log in to healthcare.gov. A senior administration official told CNN that some users, especially those who signed up "early on," have been having trouble logging in, but the administration is working on a fix. There also were conflicting reports on whether some passwords -- created in the first week or so after the launch -- were deleted.

"I'll be the first to tell you that the website launch was rockier than we would have liked," HHS Secretary Kathleen Sebelius told an audience in Cincinnati on Wednesday, during her tour to promote Obamacare. She also told CNN affiliate WLWT: "There are constant improvements under way, so that we are getting people in much more quickly."

One private-sector analysis, released by Kantar US Insights, showed that, during the first week, less than 1 percent of those who entered the registration area actually enrolled. The review, based on the findings of the Millward Brown Digital research firm, showed 9.47 million unique visitors to the federal site during the first week, including 3.72 million who entered the registration area, 1 million successfully registering and 36,000 who completed enrollment.

Observers consider the early data promising, but many say it is far too early to tell if enough young people will enroll in the exchanges to meet HHS targets.

Altogether, the agency hopes to enroll 7 million residents in the exchanges by the end of March, and it hopes that 2.7 million of those enrollees -- or 39 percent -- will be young adults, according to the Advisory Board website. In June, Sebelius said such numbers would hopefully create a "balanced risk pool."

"The best sign so far has been the huge interest in the exchanges, much beyond expectations," said Joel Ario, managing director at Manatt Health Solutions and former director of the office of health insurance exchanges at HHS.

Ario added that the "challenge will be converting that broad interest into actual purchasing of plans" and "people doing the initial purchasing are probably the people who need the coverage the most. Others will probably shop longer and purchase."